1. Field of the Invention
The field of invention relates to active seismic response control systems for use in structures, and more particularly to active seismic response control systems in which variable resistance connecting devices are provided in frames of structures to interconnect frame bodies and variable stiffness elements, or to interconnect the variable stiffness elements themselves provided in the frame wherein external vibrational forces such as earthquake tremors and wind are controlled by the use of computer technology to reduce the vibrational response of the structure to such external vibrational forces.
2. Description of the Prior Art
Applicants have heretofore proposed various types of active seismic response control systems and variable stiffness structures, each of which has a variable stiffness element in the form of a brace or a wall incorporated in the post and beam frames of a structure. The stiffness of the variable stiffness elements per se and/or the combination of a frame body and variable stiffness elements is varied responsive to analysis of the characteristics of the external vibrational forces by computer means to render the structure non-resonant relative to the external vibrational forces to attain the safety of the structure.
Prior art active seismic response control systems primarily observe and deal with the relationship between the predominant periods of seismic and/or wind vibrations and the natural frequency of the structure. Harmonic resonance of the structure during the predominant periods of external vibrations is avoided by changing the natural frequencies of the structure, thereby attenuating the response of the structure to the external vibrations. However, conventional seismic response control systems do not necessarily provide optimal control in cases where the seismic disturbances have indistinct predominant periods or a plurality of predominant periods.